Sustainable Additive Manufacturing of Polyelectrolyte Photopolymer Complexes

Abstract

polyelectrolyte materials is limited by the challenges presented in their processing. Polyelectrolyte complexes (PECs) are bulk assemblies of oppositely charged polymers, where the sites of interaction between the two species create a physical crosslink. These physical crosslinks give rise to unique phase behaviors, ultraviscosity, and a response to salinity that mimics the thermoplastic response to temperature. [12][13][14][15] Due to the dynamic nature of these ionic bonds, polyelectrolyte complexes possess unique capabilities like recyclability and self-healing that make them very attractive as compared to more conventional polymers. [4,[16][17][18][19] The unique nature of PEC bonding gives rise to an incompatibility with melt processing, making their processing extremely challenging. As a result, PECs are typically used as coatings where spatial control is only afforded in 1D (i.e. thickness of the coating) via layer-by-layer assembly. [20][21][22] Despite the lack of melt processability, progress in 2D processing of PECs has been achieved by manipulating the flow-ability of the materials via compositional variation. The thermal transition temperatures of PECs (e.g. glass transition T g ) can be tailored by PEC salinity and water content. [23][24][25] In the last decade, salinity changes have enabled extrusion of PECs. [26] While the advent of extrusion has allowed a more facile study of the properties of bulk PECs, [27,28] it has yet to lead to many practical applications outside of compounding PECs into thermoplastics. [29] Despite its early promise as a new means of processing PECs, this form of processing has largely been neglected. Relatedly, the success with extrusion of 2D profiles has not led to adaptation of 3D processing techniques such as injection molding. There is still an outstanding need for the development of 3D processing techniques for PECs to enable more widespread use of these technologies.Additive manufacturing (AM), also known as 3D printing, has seen increased popularity both industrially and in academics owing to its paradigm-shifting change of the manufacturing process. In particular, vat photopolymerization (VP) has seen significant growth due to its vast manufacturing potential and a wide variety of compatible chemistries. [30,31] There are several forms of VP additive manufacturing, but one commonality to all techniques is the formation of solid objects by exposing certain regions of a liquid resin to patterned light. The

Polybutadiene Click Chemistry: A Rapid and Direct Method for Vat Photopolymerization

“…The glass coverslip (no. 1 Corning cover glass, purchased from Sigma-Aldrich) was functionalized with 3-(trimethoxysilyl)­propyl methacrylate (98%, Sigma-Aldrich) and located over the screen, in place of the typical FEP window . For 7 mW cm –2 irradiance working curves, each square was projected for 5 s longer than the last ( i.e.…”

“…Working curve measurements of cure depth versus light exposure were performed in-printer by projecting 16 squares (1 mm × 1 mm) one at a time with incrementally longer times for each projection onto a silanized glass coverslip placed on an Asiga Max X27 405 nm DLP printer (Asiga, Alexandria, NSW, Australia). The glass coverslip (no.…”

Tailoring Properties of 3D-Printable Polyelectrolyte Photopolymer Complexes with Reactive Diluents

“…To improve mechanical properties compared to those observed in the first additively manufactured PECs, 13 a variety of commercially available comonomers were evaluated for use as reactive diluents. When mixed, polyethylenimine (PEI) undergoes an acid−base reaction with methacrylic acid (MAA) to form an ion-paired precomplexed semisolid that does not flow.…”

“…The solvent limits pot life and would evaporate after the print was complete, which caused poor optical clarity. We hypothesized the poor optical clarity was due to voids which are also responsible for the poor mechanical properties of the dry photoPECs . A common route in other photopolymer resins to mitigate high viscosities without compromising other desirable properties is to make use of molecules called reactive diluents. , These are typically monofunctional polymerizable species with similar reactivity to other components of the resin.…”

Cationic and radical polymerization using a boron–thienothiophene–triphenylamine based D–π–A type photosensitizer under white LED irradiation

“…The photopolymerization method is one of the useful methods in terms of using energy more effectively and efficiently compared to the thermal methods in polymer syntheses. [1][2][3] Visible light photopolymerizations have attracted particular interest due to their use in a variety of specific applications, such as electronics, photoresists, adhesives, printing plates, coatings, integrated circuits, 3D printing, and restorative dental materials. [4][5][6] Particularly, photoinitiated radical and cationic polymerizations have received revitalized interest as they cover a wide range of economic and ecological applications.…”